DEGRADATION OF MALIC AND TARTARIC-ACIDS BY HIGH-DENSITY CELL-SUSPENSIONS OF WINE YEASTS

High density (10(10) cfu ml(-1)) cell suspensions of 30 strains of wine yeasts representing species of Saccharomyces, Kloeckera, Candida, Schizosaccharomyces and Hansenula were examined for their ability to degrade L-malic and L-tartaric acids in a buffered assay system. Cells of Schizosaccharomyces pombe and Schizosaccharomyces malidevorans gave 95-99% degradation of L-malic acid after reaction for 48 h. Only 10-34% of the acid was degraded after reaction for 30 min. Other species did not degrade more than 35% of L-malic acid after 24-48 h. None of the yeasts degraded more than 25% of L-tartaric acid. The extent of acid degradation was not increased by culture of the cells in grape juice, inclusion of glucose or NAD in the assay system or by cell permeabilization. The specific activity of yeast cells for the degradation of malic and tartaric acids was too low for their use in membrane bioreactor systems.